Pure Mn Research Articles

Influence of Manganese on the Recrystallization Characteristics and Texture Development of Cu-29Zn Alloys

Studies regarding the recrystallization texture of brass alloys are quite complex. Previous experiments showed that the addition of the alloying elements on brass alloys affect the deformation mechanism and texture development. Alloying elements promoted the inhomogeneous deformation and resulted in a heterogeneous microstructure. During annealing, the new grains form around the shear band area and develop the random texture. This research studied the effect of Mn addition on the recrystallization characteristics and texture development of Cu-29Zn alloys. The Cu-Zn-xMn alloys were produced by gravity casting with a dimension of 110x110x6 mm3. The feeding material includes pure Cu, Zn, and Mn. The as-homogenized samples were then cold-rolled with the level of deformation of 70 % and followed by an annealing process at temperatures of 400, 500, and 600°C. Samples characterization includes chemical composition analysis, microstructure observation, hardness testing, and texture measurement. The results showed that the addition of Mn tended to reduce the rate of recrystallization and grain growth. At 70% deformation, Mn addition promoted the formation of brass and Goss texture. The presence of Mn also influenced the formation of recrystallization and annealing texture.

Microstructure and Performance of Mn-Ga/Fe-Cr-Co Magnetic Composites Fabricated by Mechanical Alloying

Mn-Ga and Fe-Cr-Co have potential use as components in exchange-coupled composite magnets. Herein, we prepared Mn-Ga composites through mechanical alloying, which was followed by sintering. During high-energy ball milling, Fe-Cr-Co powder was added into the Mn-Ga powder to form a composite. The main phases in the composites existed as pure Mn and pure Ga in the as-milled state; subsequently, these phases changed into intermetallic compounds, such as Mn3Ga and Mn0.85Ga0.15, after sintering at 385°C for 6 h. When the Fe-Cr-Co fraction increased from 0% to 20%, the coercivity (Hc) of the Mn-Ga/Fe-Cr-Co composites decreased monotonically from 8.04 kOe to 2.28 kOe; furthermore, their remanence (Mr) increased from 8.52 emu/g to 13.33 emu/g, and the maximum energy product (BH)max increased from 0.15 MGOe to 0.26 MGOe. The results obtained in this study facilitate the improvement of the magnetic properties of Mn-Ga composites for utilization in permanent magnet applications.

Ultrafine MnO2/graphene based hybrid nanoframeworks as high-performance flexible electrode for energy storage applications

Pristine MnO2 and MnO2/graphene (abbreviated as Mn and MnG) nanocomposite has been prepared through a facile hydrothermal method under mild conditions. The morphology and nanostructure of the prepared composite are individualized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Raman microscope, Brunauer–Emmet–Teller and X-ray photoelectron spectroscopy (XPS). XRD results reveal the pure tetragonal phase of α-MnO2 with the space group of I4/m. TEM images show spherical morphology for pure Mn and layered structure for MnG. The results of N2 adsorption–desorption analysis indicates the specific surface area of the prepared nanomaterials and it was found to be 92 m2/g and 134 m2/g for the pure Mn and MnG nanocomposites. The XPS spectrum shows the confining states of different elements present in the composites. Electrochemical execution of the synthesized composite electrodes was evaluated using both two and three-electrode system. We have achieved maximum specific capacitance of 1537 Fg−1 at the charging current of 20 Ag−1 with high steadiness was observed up to 6000 cycles. The fabricated ASC devices manifest a maximum energy density of 22 Wh kg−1 with long standing cyclic stability of 90.5% capacitance retention after 5000 cycles.

Structural and charge density distribution studies on Tin Oxide nanoparticles for Supercapacitor application

Pure SnO and Mn doped SnO (Mn:SnO) nanoparticles have been successfully prepared by simplest route of the hydrothermal method. Prepared nanoparticles have been characterized by various analyses to understand structural, optical, morphological, elemental composition, Photoluminescence and electrochemical behaviours. The powder X-ray diffraction pattern analysis confirms the formation of crystalline nature of pure and Mn:SnO and its tetragonal structure. Functional group and elemental composition of prepared nanoparticles are confirmed using FTIR and EDX. The electrochemical performances of the prepared materials as working electrodes are analyzed by electrochemical workstation, analyzed parameters such as cyclic voltammetry and galvanostatic charge-discharge. From this study, maximum specific capacitance (Csp) is 246.5 F g − 1 at 5 mA cm−2 is obtained. The optical energy band gap is found to be 3.17 and 2.61 eV for SnO and Mn:SnO nanoparticles, respectively.

Alkaline wet oxidation of lignin over Cu-Mn mixed oxide catalysts for production of vanillin

Abstract Alkaline wet oxidation of lignin was performed to study the effect of Cu-Mn mixed oxide catalysts on the production of vanillin at between 120–180 °C using H2O2 as an oxidizing agent. The mixed oxide catalysts were prepared by a sol-gel method with mixing ratios of Cu to Mn between 0.25 and 0.75 and characterized by XRD, XPS, N2-physisorption, SEM-EDS, and H2-TPR. The XRD and N2-physisorption analyses showed a non-stoichiometric spinel structure (Cu1.5Mn1.5O4) and a relatively high BET surface area of the mixed oxides compared with pure Cu and Mn oxides, respectively. In addition, the Cu-Mn mixed oxide catalysts exhibited better redox properties and a higher catalytic performance for lignin oxidation to vanillin and other aromatic oxygenates. Higher Cu contents in the mixed oxide catalysts promoted the over-oxidation of vanillin producing vanillic acid along with the formation of more surface oxygen species on the catalyst surface. Finally, a possible reaction pathway for the catalytic conversion of lignin to vanillin was proposed.

Genesis and 40Ar/39Ar dating of K-Mn oxides from the Stavelot Massif (Ardenne, Belgium): Insights into Oligocene to Pliocene weathering periods in Western Europe

The occurrence of Ordovician Fe-Mn-rich sediments (Ottré Formation, Salm Group) in the Stavelot inlier (NE Ardenne, Rhenish Massif, Belgium) has drawn the attention of geoscientists for more than one century, as they contain natural “coticule” whetstones and numerous weathered Mn deposits. Two locations expose the Fe-Mn-bearing rocks: the Chevron area to the north is located at an altitude of 230–380 m, and the Salmchâteau at 480–570 m. The Mn-bearing sediments have undergone greenschist facies metamorphism in relation to the Caledonian and Variscan orogenesis, and more recently weathering processes, transforming the early mineral assemblages (mainly rhodochrosite and/or kutnohorite, spessartine, muscovite, chloritoïd, andalusite, hematite) into secondary Mn oxides,—hydroxides and—oxyhydroxides (cryptomelane, nsutite, lithiophorite, manganite, pyrolusite), clays (mainly kaolinite) and Fe oxides (goethite). In this paper, we investigate the weathering processes of these Mn-rich rocks by i) new mineralogical, petrographical and geochemical data, and ii) new 40Ar/39Ar geochronology of K-Mn oxides.Petrographical and geochemical data indicate that rhodochrosite (and/or kutnohorite) is the main source of Mn, from which Mn oxides have precipitated. Spessartine and other Mn-silicates have poorly contributed to the Mn mobilization. Pure Mn oxides, namely manganite, nsutite, and pyrolusite, successively replace rhodochrosite under increasing O2 conditions due to the weathering fluids, while the formation of cryptomelane and then lithiophorite in veins is associated to the recombination of K+, Li+ and Al3+ released from the phyllosilicate matrix of the host slate, probably in relation with sligh pH changes. This multistage character of weathering processes is well identified in the Salmchâteau area, where weathering conditions are stronger than in the Chevron area because of the elevation. This also positions the Mn levels close to the roll front within the lower saprolite and the fissured horizon, respectivelly. Such differences in the weathering grade of these areas determined a weathering-type deposit in the Salmchâteau area and a carbonate-hosted sedimentary deposit in the Chevron area. Weathering deposits are accompanied by an enrichment in Mn and associated transition metals (As, Co, Cu, Ni). Dating of pure cryptomelane samples corroborate the multistage character of the ore and yield at least four weathering stages: Chattian (26.33 ± 0.17 Ma), Aquitanian (22.2 ± 0.6 and 20.0 ± 0.2 Ma), Serravalian-Tortonian (11.79 ± 0.10 to 10.12 ± 0.18 Ma) and Pliocene or younger (5.30 ± 0.76 and 4.11 ± 0.57 Ma). A relatively continuous weathering of the Massif since the late Oligocene, or older weathering phases, cannot be excluded as the upper part of the saprolite (and laterite) have been removed. As climatic conditions evolve from tropical to temperate by the Oligocene, the uplift of the Ardenne is probably the main factor triggering the development of weathering mantle, together with the increasing seasonality and high precipitation. These ages with others obtained in supergene ores of Western European massifs define a long-lasting weathering wave since the late Oligocene until the uppermost Neogene. The absence of older periods in the 40Ar/39Ar record of these deposits indicates that the upper part of the weathering mantle was recently stripped and limit their economic interest.

Ab initio study of optoelectronic and magnetic properties of Mn-doped ZnS with and without vacancy defects

The effect of vacancy defects on optoelectronic and magnetic properties of Mn-doped ZnS have been systematically investigated using first principle approaches. A single Mn substitution at Zn site induces a spin-polarized ground state in pure ZnS with total magnetization 5 . Our results for magnetic coupling show that the coupling between Mn spins in pure Mn doped ZnS is antiferromagnetic under the super-exchange mechanism. The existence of native defects has a great influence on the magnetic ground state of Mn-doped ZnS. In particular, a p -type defect such as Zn vacancy play a crucial role in stabilizing ferromagnetic ground state while n-type defect, such as S vacancy, has no effect on the magnetic ground state i.e. the interaction between two Mn spins with S-vacancy remain antiferromagnetic. Furthermore, optical properties such as dielectric functions, absorption coeffiecients, reflectivity and transmissitivity for Mn doped systems with and without vacancy defect were also studied, and we found that an absorption peak was obtained in the infrared region which is attributed to the defect states introduced by Zn vacancy in the system. In a S-vacancy defect system, the peaks in the near infrared and visible region are due to donor states introduced by S vacancy defect and these peaks are produced by electrons flipping from a spin up state to a spin down state. Finally, we also correlated the magnetic interactions with the d–d optical transition in pure Mn-doped ZnS and found that the d–d transitions during optical absorptions are red shifted and blue shifted in FM and AFM coupled Mn ions pair, which is in good agreement with the experimental observations. This study may help to understand the behavior of optical and magnetic properties of DMS under vacancy defects.

Corrosion Behavior of Cocrfemnni High Entropy Alloy in Acidic Solutions

High entropy alloys (HEAs) are new concept in alloy design. HEAs contain five or more metallic elements in equimolar or near-equimolar ratios. Although HEAs are multi-component alloys, they form single-phase solid solutions. HEAs have outstanding properties that were not found in conventional alloys such as Fe-base alloys. CoCrFeMnNi alloy, one of the most remarkable HEA, is expected to exhibit high corrosion resistance. The mechanism of corrosion resistance of CoCrFeMnNi alloy could be applied to improve the corrosion resistance of conventional Fe-Cr-Ni stainless steels. Therefore, it is important to clarify the corrosion mechanism of CoCrFeMnNi alloy. In this study, the equiatomic CoCrFeMnNi alloy was prepared as the specimens. CoCrFeMnNi alloy was made by arc melting. The samples were heated to 1523 K and hot-rolled to thickness of 2 mm. After solution treatment at 1473 K (2h, W.Q.), the surfaces of the specimens were successively polished with a diamond paste down to 1 µm. Potentiodynamic anodic polarization curves were measured in deaerated 1 M H2SO4 at 298 K to elucidate the corrosion behavior of CoCrFeMnNi alloy. As a reference, polarization curves for pure Co, Cr, Fe, Mn, and Ni were measured. The surfaces of the specimen, with the exception of the electrode area (10mm×10 mm), were covered with epoxy resin and paraffin. The measurements were performed in a conventional three electrode cell. The reference electrode was Ag/AgCl (3.33 M KCl) and the counter electrode was a Pt plate. The results of potentiodynamic anodic polarization curves are shown in Fig. 1. In the case of CoCrFeMnNi alloy, active state, passive, trans-passive, secondary passive, and O2 evolution regions appeared. Comparing with CoCrFeMnNi alloy and each pure metal, corrosion reactions of CoCrFeMnNi alloy were discussed. Figure 1

Extremely Large Non-equilibrium Tunnel Magnetoresistance Ratio in CoRhMnGe Based Magnetic Tunnel Junction by Interface Modification.

Equiatomic quaternary Heusler compounds (EQHCs) generally have the advantages of high Curie temperature, large spin polarization and long spin diffusion length, and they are regarded as one of the most promising candidates for spintronics devices. Herein, we report a theoretical investigation on an EQHC CoRhMnGe based magnetic tunnel junction (MTJ) with (i) MnGe-terminated interface and (ii) modified pure Mn terminated interface, i.e., MnMn-terminated interface. By employing first principle calculations combined with non-equilibrium Green's function, the local density of states (LDOS), transmission coefficient, spin-polarized current, tunnel magnetoresistance (TMR) ratio and spin injection efficiency (SIE) as a function of bias voltage are studied. It reveals that when the MTJ under equilibrium state, TMR ratio of MnGe-terminated structure is as high as 3,438%. When the MTJ is modified to MnMn-terminated interface, TMR ratio at equilibrium is enhanced to 2 × 105%, and spin filtering effects are also strengthened. When bias voltage is applied to the MTJ, the TMR ratio of the MnGe-terminated structure suffers a dramatic loss. While the modified MnMn-terminated structure could preserve a large TMR value of 1 × 105%, even bias voltage rises up to 0.1 V, showing a robust bias endurance. These excellent spin transport properties make the CoRhMnGe a promising candidate material for spintronics devices.

An environmentally friendly closed loop process to recycle raw materials from spent alkaline batteries

Abstract This study proposes a nearly-zero waste and simple hydrometallurgical process for efficiently recycling the main metal components (manganese-Mn and zinc-Zn) from spent alkaline batteries waste with a high grade of purity. The process is based on the novel combination of a single microwave-assisted reductive acid leaching step followed by a single solvent extraction (SE) step for simultaneous extraction and purification of both metals, respectively. An optional ion exchange (IE) step to improve the purity of the Mn solution may be included, if desired. When compared with conventional leaching methods, microwave-assisted leaching decreased substantially the reaction time whilst maintaining high leaching performance for both metals. Subsequently, a single SE step, using Cyanex 302, resulted in a high pure aqueous Mn solution and a high concentrated and pure Zn solution after its complete stripping from the organic phase. Additional purification of the Mn solution by IE, using a bispicolylamine resin, resulted in a highly pure Mn solution. In conclusion, this work demonstrates a novel and optimized process for recycling almost all metal content from spent alkaline batteries into proper secondary raw materials for production of new batteries.

Combining KMnO4 pre-oxidation and bioaugmented sand filtration to simultaneously treat cyanobacterial bloom lake water and released Mn(II)

Harmful cyanobacterial blooms negatively impact lake ecosystems and affect drinking water treatment when using bloom source water. To guarantee effluent water quality, pre-oxidation is frequently used to break down cyanobacteria. However, the release of contaminants from cyanobacterial cells can be an issue during treatment. Here we proposed a novel drinking water treatment technique based on the characteristics of cyanobacterial blooms in an eutrophicated lake. Using molecular flow cytometry and 16S rRNA sequencing we compared the microbial community biomass and composition between cyanobacterial bloom and non-bloom events. Results demonstrated a cyanobacterial composition shift from an unidentified Nostocaceae genus to Microcystis and a 21-times increase in cyanobacterial biomass after a bloom event. Based on these findings, KMnO4 was selected as a pre-oxidation agent for lake water treatment. Batch experiments revealed that the addition of KMnO4 did not increase the concentration of microcystin-LR but did increase the release of Mn(II) into water. To eliminate this issue, we applied a bioaugmented sand filtration process. Using pure Mn(II)-oxidizing bacterium Pseudomonas sp. QJX-1 and biofilmed quartz sands from an existing sand filter, we demonstrated that bioaugmented sand filtration transformed Mn(II) to biogenic manganese oxide, which exhibited strong oxidation and adsorption capabilities for organics and metalloids. Hence, we propose an alternative KMnO4 pre-oxidation plus bioaugmented sand filtration system to improve bloom water treatment.

Geochemical Stability of Dissolved Mn(III) in the Presence of Pyrophosphate as a Model Ligand: Complexation and Disproportionation.

Dissolved Mn(III) species have recently been recognized as a significant form of Mn in redox transition zones, but their speciation, stability, and reactivity are poorly understood. Besides acting as the intermediate for Mn redox chemistry, Mn(III) can undergo disproportionation producing insoluble Mn oxides and aqueous Mn(II). Using pyrophosphate(PP) as a model ligand, we evaluated the thermodynamic and kinetic stability of Mn(III) complexes. They were stable at circumneutral pH and were prone to (partial) disproportionation at acidic or basic pH. With an initial lag phase, the kinetics of Mn(III)-PP disproportionation was autocatalytic with the produced Mn oxides promoting the disproportionation. X-ray diffraction and the average Mn oxidation state indicated that the solid products were not pure Mn(IV) oxides but a mixture of triclinic birnessite and δ-MnO2. Addition of synthetic analogs of the precipitates eliminated the lag phase, confirming their catalytic roles. Thermodynamic calculations adequately predicted the stability regime of Mn(III)-PP. The present results refined the constant for Mn(PP)25- formation, which allows a consistent and quantitative prediction of equilibrium speciation of Mn(III)-Mn(II)-birnessite with PP. A simple and robust model, which incorporated the thermodynamic constraints, autocatalytic rate law, and verified reaction stoichiometry, successfully simulated all kinetic data.

Density functional theory study of structural and thermodynamical stabilities of ferromagnetic MnX (X = P, As, Sb, Bi) compounds

Density functional theory (DFT) calculations for deriving enthalpies of formation H for ferromagnetic MnX (X P, As, Sb, Bi) compounds were made for the two competing structures, hexagonal and orthorhombic . Standard calculations were performed by using pseudopotentials with the generalized-gradient-approximation (PBE) as exchange-correlation functional. Enhanced exchange-correlation interactions were included by making use of a so-called DFTU approach which requires as a parameter. Application of PBE potentials for all compounds and elementary phases (all-PBE) resulted in negative values of H for MnP and MnAs in both structures whereby the result for MnP agrees very well with experiment. For MnSb and MnBi the all-PBE calculation gives a positive nonbonding H disagreeing with experiment. To overcome this discrepancy for MnSb and MnBi a DFTU ansatz was employed for all compounds and elemental Mn. The values for ranging between 0.7 for MnBi and 1.4 eV for MnAs were determined by fitting the DFT results to measured data of H. As a reference for pure Mn the -Mn phase was taken with eV by which choice the experimental volume is fitted. Atomic volumes and ionicities were derived applying Bader’s concept resulting in ionicities of Mn less than .

Efficacy of photoluminescence and photocatalytic properties of Mn doped ZrO2 nanoparticles by facile precipitation method

Pure ZrO2 and Mn (0.02, 0.04, 0.06, 0.08 M) doped ZrO2 nanoparticles were successfully prepared by chemical precipitation method. The structural, optical, morphological and electronic properties were determined using XRD, UV-DRS, PL, FE-SEM, TEM and XPS techniques. The XRD pattern of pure and Mn doped ZrO2 shows the formation of t-tetragonal phase and shifting of tetragonal phase to monoclinic phase. The energy gap of pure and Mn doped ZrO2 nanoparticles were computed by UV-DRS spectroscopy. The energy gap value of pure and Mn doped ZrO2 nanoparticles decreased from 5.12 to 2.46 eV with increase of manganese concentration. X-ray Photoelectron spectroscopy (XPS) affirmed the presence of Zr4+ and Mn2+ ion in prepared nanoparticles. PL spectra of the pure and Mn doped ZrO2 nanoparticles exhibited oxygen vacancies. The photocatalytic actvity of Mn (0.08 M) doped ZrO2 nanoparticles was successfully sought on photo degradation of Methyl violet and Methylene blue under sunlight irradiation.

Mn3O4 with different morphologies tuned through one-step electrochemical method for high-performance lithium-ion batteries anode

A simple, green, efficient, and controllable electrochemical potential perturbation method has been developed to synthesize Mn3O4 nanomaterials. No toxic or explosive chemicals are used during the fabrication process. Taking pure Mn metal as the working electrode and 2 M KCl aqueous solution as the electrolyte solution, the Mn3O4 products with rod-like, spherical-like and mixed structures can be obtained through cyclic voltammetry technology under rapid scan rates of 5, 200 and 50 V s−1 within a potential range of −2.0 to 2.0 V (vs Saturated calomel electrode, SCE), respectively. Rapid and repeated redox treatment of Mn metal surface accompanying intense oxygen and hydrogen evolution will lead to the dispersion of Mn metal and the formation of the Mn3O4 nanomaterials. The lithium-ion storage behaviors of these as-fabricated Mn3O4 nanomaterials have been studied contrastively, showing that the spherical-like Mn3O4-S nanoparticles with the highest Li-ion chemical diffusion coefficient display the best cycling stability and rate capability. As a consequence, it shows an excellent specific capacity of up to 780 mAh g−1 after 250 cycles a high rate of 1000 mA g−1 and a good rate capability of 895, 798, 722, 683, 601 and 530 mAh g−1 at current densities of 200, 500, 800, 1000, 1500 and 2000 mA g−1, respectively. This work is of importance for energy storage as it provides a new and efficient electrochemical way for the fabrication of anode materials for the next-generation LIBs with outstanding electrochemical performances.

Electrodeposition of Fe, Co, Mn and Their Alloys from Choline Chloride/Urea Based Deep Eutectic Solvents

Despite their industrial use for many decades, there is still desire and opportunity to improve the properties of soft magnetic materials. Applications such as hard drive write heads must attain higher saturation magnetization and low coercivity in order to maintain the ability to write to increasingly dense storage media[1]. Electrodeposition is often the favored fabrication method for such soft magnetic films due to its several advantages such as fast deposition rate, ease of growth on arbitrary shaped or recessed surfaces, and simplicity of orienting film anisotropy[2]. However, it is fairly limited in the number of different elements that can be deposited in high quality. In the past several years, room temperature ionic liquids, the current generation also being known as deep eutectic solvents (DES), have become an attractive alternative to traditional aqueous deposition baths. These solvents avoid the hydrogen generation that often reduces deposit quality and efficiency in aqueous baths, and enable the incorporation into the deposit of metals with more negative deposition potentials than are viable in aqueous baths. Despite significant progress in literature on the electrodeposition of various material from DESs, their suitability for improving characteristics of magnetic films is relatively little-studied[3]. This work studies the deposition behavior of Fe, Co, and FeCo ferromagnetic alloys from the DES formed of a 1:2 mole ratio of choline chloride and urea (ChCl-urea). Deposited films are then characterized to determine their morphology, crystal structure, and magnetic properties. Mn, which has been predicted to increase the magnetization of FeCo materials[4], has been incorporated to form a tertiary FeCoMn ferromagnetic alloy, and its effects of the film properties are determined. Initial voltammetric studies (Fig. 1) and depositions show that deposition of Fe-Co from ChCl-urea proceeds by induced codeposition, wherein Fe deposition is promoted by Co, allowing the alloy film to be obtained at potentials less negative than required for pure Fe. Increasing the deposition overpotential leads to higher Fe content in the film, and a mass transfer limit is quickly reached for both depositing species at which the film composition no longer depends on overpotential. Composition of the deposit is easily controlled by changing the metal ion concentration in the bath. Mn is also found to deposit by an induced codeposition mechanism with Fe-Co, wherein it can be incorporated into FeCo films in small amounts at an underpotential to pure Mn electrodeposition. The incorporation of Mn in alloy films is constant at around 3 wt. % when depositing in underpotential conditions. The effects of several deposition conditions including temperature, metal ion concentrations, and bath agitation, were studied and will be discussed in the presentation.

Facile microwave-assisted synthesis of Al:Mn co-doped PbI2 nanosheets: structural, vibrational, morphological, dielectric and radiation activity studies

Abstract Herein, we report a successful development of nano-scale pure and Al and Mn co-doped PbI2 using facile microwaveassisted route. Structural study was done through X-ray diffraction analysis of grain size, dislocation density and lattice strain. The crystallite size was found to vary from 28 nm to 40 nm due to Al:Mn co-doping in PbI2. The presence of various vibrational modes was confirmed by FT-IR spectroscopy and red shifting was observed in peak positions compared to the bulk. Surface morphology, examined using a scanning electron microscope, confirmed the formation of single crystal nanosheets of a thickness in the range of 10 nm to 30 nm. The single crystal nanosheets were found to be transformed to large area nanosheets due to the doping. Enhancement in dielectric constant from ~7.5 to 11 was observed with increasing Al doping concentration. Linear attenuation coefficient was calculated and showed the enhancement of blocking gamma rays with increasing doping concentration. Its value was found to increase from 7.5 to 12.8 with the doping. The results suggest that the synthesized nanostructures can be used for detection and absorption of gamma rays emitted by 137Cs and 241Am sources.

Rare earth-free hard magnetic microwires

Novel microwires of composition MnBi were obtained by means of quenching and drawing technique having a metallic nucleus of 50 μm diameter. Phase distribution analysis showed a composite microstructure comprising extensive zones of the ferromagnetic hexagonal MnBi phase (of up to 12 μm), interspersed within a matrix of diamagnetic Bi and some inclusions of pure Mn varying between 1 and 2 μm in length. A coercive field in excess of 4000 Oe was measured. Coercivity mechanism is described in terms of nucleation of reverse domains, for which the interface MnBi/Bi largely determines the hard magnetic response of the composite microwire.

Microstructure, optical, dielectric and electrical characterizations of Mn doped ZnO nanocrystals synthesized by mechanical alloying

Mn doped ZnO nanocrystals are successfully synthesized, for the first time, by mechanical alloying the stoichiometric mixture of pure ZnO and Mn powders. The structural and compositional analyses are carried out using X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM). Rietveld's analysis of the XRD patterns confirms the formation of single phase wurtzite Zn0.90Mn0.10O nanostructures. Different structural and microstructural parameters such as lattice parameters, crystallite size, r.m.s. strain, stacking faults etc. have been ascertained from the Rietveld analysis. UV–vis spectra are analyzed for band gap measurement and photoluminescence (PL) emission spectra have also been analyzed for estimating different structural defects and optical features of the samples. Temperature dependent dc electrical behavior is studied and the conduction mechanism has been explained by the Godet variable range hopping theory (3D G-VRH). Complex impedance analysis is used to distinguish the grain and grain boundary contribution to the system and it suggests the dominance of grain resistance in the synthesized samples. The dielectric behavior, electric modulus and ac conductivity are studied as a function of temperature (573–773 K) and frequency (100 Hz to 3 MHz). The optical and electrical characterizations predict that the synthesized materials have potential for use in optoelectronics applications.

“One-sample concept” micro-combinatory for high throughput TEM of binary films

Phases of thin films may remarkably differ from that of bulk. Unlike to the comprehensive data files of Binary Phase Diagrams [1] available for bulk, complete phase maps for thin binary layers do not exist. This is due to both the diverse metastable, non-equilibrium or instable phases feasible in thin films and the required volume of characterization work with analytical techniques like TEM, SAED and EDS. The aim of the present work was to develop a method that remarkably facilitates the TEM study of the diverse binary phases of thin films, or the creation of phase maps. A micro-combinatorial method was worked out that enables both preparation and study of a gradient two-component film within a single TEM specimen. For a demonstration of the technique thin MnxAl1−x binary samples with evolving concentration from x = 0 to x = 1 have been prepared so that the transition from pure Mn to pure Al covers a 1.5 mm long track within the 3 mm diameter TEM grid.The proposed method enables the preparation and study of thin combinatorial samples including all feasible phases as a function of composition or other deposition parameters. Contrary to known “combinatorial chemistry”, in which a series of different samples are deposited in one run, and investigated, one at a time, the present micro-combinatorial method produces a single specimen condensing a complete library of a binary system that can be studied, efficiently, within a single TEM session. That provides extremely high throughput for TEM characterization of composition-dependent phases, exploration of new materials, or the construction of phase diagrams of binary films.